Threading tool



Patented Aug. 26, 1941 UNITED lSTATES PATENT FFICE 2,253,491 THREADING 'rooL l Harding F. Bakewell, San Marino, Calif. Application February 7, 1940, Serial No. 317,687

9 Claims.

This invention is a threading tool, either a tap having an exterior cutting-thread for internally threading the work or a die having an interior cutting-thread for externally threading the work.

1t is an object or the inventin to interrupt vthe circumference of .the cutting-thread by longitudinal iiutes of appreciably greater number than heretofore employed.' More particularly, it is an object of the invention yto provide longitudinal iiutes on the order of approximately twelve or more per circumference.

It is a further object of .the invention to provide longitudinal flutes of a width circumferentially of the cutting-.thread approximately equal to arcuate lengths of the cutting-thread between next adjacent flutes.

More particularly, it `is an object of the invention to provide longitudinal ilutes on the.

order of approximately twelve or more per circumference, with approximately equal Width of the flutes and arcuate length of the cuttingthread between next adjacent flutes.

It is a still further object of the invention to adapt the cutting-thread for reversal for use of either end of the .cutting-thread.

More particularly, it is an object of the invention to provide a cutting-edge and a relievededge for each arcuate length of the cuttingthread which is between next adjacent flutes, with that portion of the cutting-thread which is between one of its ends yand medlally of its length having its cutting-edges and its relievededges reversed with relation to the cutting-edges and the relieved-edges of that portion of the cutting-thread which extends from medially of its length to its opposite end.

-It is a still further object of the invention to adapt the cutting-thread for readily detachable mounting on a tool shank which is in turn adapted for mounting in any usual holder; the detachable cutting-thread, in the case of a tap,

* comprising an annulus having an exterior tapping thread and adapted for reception of the annulus on the tool shank, and in the'case of a die, comprising an annulus adapted for reception of an internally threaded die in one end thereof and adapted for reception of its other end on the tool shank.

It i-s a still further object of the invention to provide a longitudinally iloating mounting for the thread-cutting unit on the tool shank.

More particularly; it is an ob-jectof the inveni tion to mount the thread-cutting unit on the tool shank vfor longitudinal displacement relative thereto, with the thread-cutting unit xed against rotation relative to the tool shank when longitudinally displaced responsivetc pressure exerted by thread-cutting engagement with the work; and with the thread-cutting unit, when longitudinally displaced in the opposite direction,

adapted for free rotation relative to ythe tool shank in the direction of thread-cutting relative rotation of the tool and the work, but xed against rotation relative to the tool shank in the opposite direction.

Further objects of the invention will be readily understood from the following description of the accompanying drawing which illustrates various embodied in a tap, showing conventional mounting for the shank of the tap.v

Fig. 2 is an venlarged side elevation of the tap and its shank, partly in axial section.

Fig. 3 is a transverse section on the line 3-3 of Fig. 2.

.- Fig. 4 is a side elevation of the invention es embodied in a die, with the thread-cutting unit in axial section.

As embodied in a tap, the cutting-thread is an exterior thread l on an annulus 2, with the circumference of the cutting-thread interrupted by longitudinal flutes 3. A relatively large number of flutes are provided, as distinguished from y prior practice of employing utes on the order jacent ilutes.

of four to six per circumference, the number of flutes being on the order of approximately twelve or more per circumference. The utes are equidistantly spaced, forming uniform v.arcuate lengths of the cutting-thread between next adrelatively ,narrow `width compared with the length ofthe interrupted arcs of the cut-tingthread, are preferably of approximately the same width as the length of these interrupted arcs.

In the Adirection of thread-cutting relative rotation of the tool and the work (indicated by arrow A) the leading -edges of the arcs of the cutting-thread are preferably undercut so as to form cutting-edges 4, and the trailing edges of the arcs of the cutting-thread are preferably chamfered so as to form relieved-edges 5. At the` end `of'the tool .which initially engages the work 'I'he flutes, instead of `being' of the thread I is preferably chamfered asshown at 6 for starting the thread-cutting operation.

By the ,construction as thus described, a relatively large number of cutting-edges 4 are adapted for cutting engagement with the work at each rotation of the tool relative to the work, as is particularly advantageous when the chamfer 6 is comparatively short so that the full cutting diameter of the thread I is attained before many' relative rotations of the tool have been made, the improved construction providing for appreciably increasing the number o'f cutting engagements at edges 4 by the time full cutting diameter is reached. Furthermore, the cutting-thread clears the work a relatively large number of time: during each rotation of the tool relative to the work, i. e. at each of the ilutes 3, thereby adapting .the tool for thread-cutting with each arcuate length of the cutting-thread concentric with the axis of rotation throughout its entire length from its leading to its trailing edge as indicated at 'I, instead of necessitating each arcuate length being relieved from true concentricity toward its trailing edge.

For convenient and economical replacement of the cutting thread .when it becomes worn, the annulus 2 is .adapted for reversal on thel tool shank and the thread i extends the length of the annulus for thread-cutting engagement with the work irrespective of which end of the thread is the leading end. For this purpose, one side of each of the utes 3 has cutting-edges 4 in longitudinal alinement along the same, from the chamfered end S to medially of Ithe length of the thread I, and has relieved-edges I 05 (similar to the edges 5 previously described) in longitudinal alinement along the same from medially of the length ot the thread to its opposite end. In similar manner, the other side of each of the utes 3 has relieved-edges 5 in longitudinal alinement along the same, from the chamfered end 6 to medially of the length of the thread i, and has cutting-edges I 04 (simil-ar to the edges 4 previously decribed) `in longitudinal alinement along the same from medially of` the length of the thread to its opposite end. ri'he end of the thread which is opposite its chamfered end 6, is similarly chamfered as shown at |06.

The thread-cutting annulus 2 is adapted for mounting on a shank IU which is in turn adapted for mounting in any usual holder, e. g. a chuck. turret head, etc. For purpose of illustration, the shank I0 is shown xed against rota- I4 may project from the shoulder 'I2 longitudinally `of the shank IU, for reception in cooperating bores I5 or II5 which are provided in the respective ends of the annulus 2. The threadcutting annulus may thus be readily slipped onto the end I3 of the shank III so as to engage the shoulder I2, with the pins I4 received in their cooperating bores and locking the annulus against rotation relative to the tool shank, and with either end of the thread I positioned for thread-cutting engagement with the work.

When the annulus 2 is longitudinally displaced on its bearing `I3 so as to no longer abut the shoulder I2, it remains fixed against rotation relative to the tool shank as long as the pins I4 are received in the bores I5 or II5, but this locking engagement is released as soon as relative longitudinal displacement of the annulus 2 shifts it clear of the pins I4. The annulus 2'is then free for rotation on its bearing I3 in the directionv (indicated by arrow A) of thread-cutting relative rotation of the tool and the work; but

means are provided for locking the annulus 2 against rotation on its bearing I3 while permitting free longitudinal displacement relative thereto, when the direction of relative rotation of the tool and the work is opposite to that indicated by arrow A, i. e. in the direction for threaded. withdrawal of the tool' from the work.

As an instance, a one-way clutch is provided periphery of the bearing I3 and held against tion in a turret head II for thread-cutting relative rotation of the tool and the work by rotating the work (not shown), with, the tool and the work adapted for relative axial feed by axial displacement of either thel turret head or the l work.

The thread-cutting annulus 2 is mounted on ythe shank I 0 for ready reversal for use of either end of thethread i, and is adapted for longitudinal displacement relative to the shank I0 with its longitudinal displacement limited in that direlative to the shank Il). For this purpose, pins radial displacement from its groove as shown at I. The roller isadapted for lateral play in its groove, with the base of the groove inclined as shown at I9.

When relative rotation of the annulus 2 and the shank I0 is in the direction indicated by arrow A, frictional contact of the roller I6 with the bore of the annulus laterally shifts the roller in its groove to the deep side of the groove, in which position the periphery of the roller is clear of the bore of the annulus, thereby permitting free relative rotation of the annulus and the tool shank. When relative rotation of th'eannulus 2 and the shank I0 is in the direction opposite to that indicated by arrow A, frictional contact of the roller I6 with the bore of the annulus' laterally shifts the roller in its groove to the shallow side of the groove, in which position the periphery of the roller projects beyond the periphery of the bearing I3 for binding engagement with the bore of the annulus, thereby fixing the annulus againstrotation relative to the tool shank.

In operation, with the annulus 2 mounted on the bearing I3 against the shoulder I2 so that the pins I4 nx the annulus against rotation relative to the tool shank, and with the work and the tool shank relatively rotated in thread-cutting direction as indicated by arrow A, relative axial feed of the tool shank toward the work axially feeds the annulus .2 for threading the work by the relatively rotating thread I; and as soon as the thread has been started, its threaded engagement *.viththe relatively rotating annulus 2 maintains thread-lead of the annulus for continuing the thread-cutting operation. In other words,

ward the work is arrested, threaded engagement of the annulus 2 with the thread which has been out, thus continues the threading operation until longitudinal displacement of the annulus 2 relative to the tool shank I0 clears it of the pins I4, whereupon the annulus 2 is free for rotation relative to the tool shank and will thus rotate with the threaded work, thereby arresting the threading operation irrespective of continued relative rotation of the tool shank and the work.

When the tool shank and the work are then relatively rotated in the opposite direction, the roller I 6 fixes the annulus 2 against rotation relative to its bearing I3 while leaving the annulus free for longitudinal displacement relative to said bearing. The annulus 2 and the Work ,are thus relatively rotated in the direction opposite to that indicated by arrow A, for threaded retraction of the annulus from the Work by its threaded engagement with the thread which has been cut. In other words, while being retracted from'the work the annulus 2 is adapted for floating threadlead relative to the shank I0, responsive to its threaded engagement with the threaded Work, and free of positive retractive feed of the shank I0, the retractive feed of the tool shank Abeing employed merely for clearing its shoulder I2 of the annulus 2 during threaded retraction of the -annulus from the work.

The annulus 2 is of relatively light material such as an aluminum alloy, and since it is free iioating relative to its shank I0 While threading the work and during retraction from the threaded Work, the longitudinalpressure against the cut ythread is merely that resulting from thread-lead v`of this relatively light annulus, exclusive of the weight of the relatively heavy tool shank II),

thereby threading the work without distorting the cut thread.

As embodied in a die for externally threading the Work (as illustrated at Fig. 4), the construction is the same as previous described except that the cutting-thread is formed in the bore of an auxiliary annulus which is detachably mounted in the bore vof the annulus which is adapted for free floating mounting on the tool shank, similar parts being indicated by the same reference numeral with the exponent a.

The annulus 2a is bored at one end as shown atr the bore of the annulus 22, the thread being arranged as `previously described, i. e. it is'fluted as shown'at 3a, with respective ends of the thread chamfered, and with cutting-edges and relievededges at respective sides of one end of each flute, in longitudinal'alinement with relieved-edges and cutting-edges at respective sides of the opposite end of each flute. The annulus 22 is thus adapted for mounting in the bore 2I with either end of its thread la forming the leading end which is adapted for threaded engagement with the Work; and when the annulus is thus mounted in its bore 2| for use of either end of its thread it may be detachably fixed against rotation and longitudinal displacement by a set screw 23.

The annulus 2a and the auxiliary annulus 22 are of relatively light metal such as an aluminum alloy, preferably with sleeves 25- 26 fixed in the respective ends of the annulus 2a and forming the bores 20a-2|. The sleeve 25 is preferably flanged at its outer end so as to overlie the end of the annulus2a and form the surface of the annulus which is adapted to abut the shoulder I2a, and the sleeve 26 is preferably flanged at its inner end so as to abut theannulus 2a and form the shoulder of the bore 2| which is adapted for abutment by the inner end of the auxiliary annulus 22. The sleeves 25-26 may be fixed in their cooperating bores in any usual manner, preferably by shrinking them in place; and are of Wear-resisting material, preferably a metal harder than the aluminum alloy annuli 2a--22.

The operationis the same as that previously described, the thread-cutting unit 2a-22 floating onits bearing I3a for threaddead of this relatively light unit by its relative rotation and threaded engagement with the work, free of positive feed of the shank Illa which is vemployed merely for maintaining engagement of the pins I4a in their cooperating bores I5a during the thread cutting operation and for clearing the shoulder I2a of the annulus 2a during threaded retraction of the annulus from the\work. While threading the work and during subsequent retraction of the die from the threaded Work, the longitudinal pressure against the cut thread is therefore merely that resulting from thread-lead of the relatively light unit 2a-22, exclusive of the weight of the shank Ia, thereby threading the work Without distorting the cut thread,

I claim:

1. In a threading. tool, an annulus having a cutting-thread, longitudinal flutes defining arcuate lengths of the cutting-thread between circumferentially next adjacent flutes, and means for rotatably supporting the annulus, the annulus being adapted for reverse mounting relative to the supporting means for use of either end of the cutting-thread, the arcuate lengths of the cutting-thread having cutting-edges and relieved-edges at their respective ends, with the cutting-edges and the relieved-edges of those arcuate lengths of the cutting-thread which are between one end of the thread and medially of its length, circumferentially reversed with relation to the cutting-edges and the relieved-edges of those arcuate lengths of the cutting-thread which are between the opposite end of the thread and medially of its length.

2. In a threading tool, an annulus having a cutting-thread, a tool shank the external periphery of the .shank and the internal periphery of the annulus forming cooperating bearing 'surfaces adapting the annulus for rotatable Imounting on the shank with the annulus adapted for longitudinal displacement relative tothe shank, Ameans for fixing the annulus against rotation relative to the shank when relatively 'longitudinally displaced in one direction, said means permittingrelative longitudinal displacement of the annulus in the opposite direction and adapted to release the annulus for rotation relative to the shank when the annulus is longitudinally displaced .in said opposite direction, and a clutch comprising a groove in one of the cooperating bearing surfaces tapering in depth circumferentially of the annulus and shank, and a roller in saidtapering groove for binding the annulus against rotation relative to the shank in one direction but releasing the annulus for rotation relative to the shank in the opposite direction, said clutch permitting longitudinal displacement of the annulus relative to the shank. l,

3. In a threading tool, a tool shank adapted for mounting of one end of the shank in a holder, an annulus of relatively light material and having a cutting-thread, the external periphery of the opposite end of the shank 'and the internrl periphery of the annulus forming cooperating bearing surfaces adapting the annulus for rotatable mounting on said opposite end of the shankwith the annulus adapted for longitudinal displacement relative tothe shank, cooperating` means between said opposite end of the `shank and the annulus for fixing the annulus against rotation relative to the shank when relatively longitudinally displaced in one direction,

vsaicl means permitting relative longitudinal displacement of the annulus in the opposite direction and adapted to release the annulus for rotation relative to the shank when the annulus is longitudinally displaced in said opposite direction, and a clutch comprising a groove in one of the cooperating bearing surfaces tapering in depth circumferentially oi the annulus and shank, and a roller in said tapering groove for binding the annulus against rotation relative to the shank in one direction but releasing the annulus for rotation relative to the shank in the opposite direction, said clutch permitting longitudinal displacement of the annulus relative to the shank.

4. In a threading tool, a tool shank having a shouldered bearing-end, a pin projecting longitudinally from the shoulder, an annulus having a cutting-thread, the external periphery of the bearing-end of the shank and the internal periphery of the annulus forming cooperating bearing surfaces adapting the annulus for sliding journaled reception on the bearing-end of the shank, the annulus having a bore adapted for reception of the pin, and a clutch comprising a groove in one of the cooperating bearing surfaces tapering in depth circumferentially of the annulus and shank. and a roller in said tapering groove permitting longitudinal displacement of the annulus relative to the shank and fixing the annulusagairist rotation relative to the shank in ohe'ldire'ctioii b'ut automatically releasing the annulus for -rotation relative to theshank in the opposite direction. l

5. In a threading too1, a tool shank having a shouldered bearing-lend, a pin projecting longitudinally from the shoulder, an annulus adapted for ,sliding journaledreception onthe bearingend of the shank with the annulus in either of axially reversed positions, a cutting-thread at the external periphery of the annulus adapted for thread-cutting by the respective ends oi' the thread when the annulus is in its respective axially reversed positions, each end of the annulus having a bore adapted for respective reception of the pin when the annulus is in its respective axially reversed positions, a groove in the external periphery of the bearing-end of the shank tapering in depth circumferentially of the shank, and a roller in the tapering groove permitting longitudinal displacement of the annulus relative to the shank and xing the annulus against rotation relative to the shank in one direction but automatically releasing the annulus for rotation relative to the shank in the opposite direction.

6. In a threading, tool, an annulus having a cutting thread interrupted at circumferentially spaced points so as to denne arcuate lengths of the cutting-thread between circumferentially next adjacentrinterruptions, the annulus being adapted for axially-reversible rotatable mounting for use of one end or the other of the cutting thread of the rotatable annulus, the arcuate lengths of the cutting-thread having cutting-edges and relieved-edges at their. respective ends. with the cutting-edges and the relieved-edges of those arcuate lengths oi' the cutting-thread which are between one end of the thread and medially of its length, circumferentially reversed with relation to'the cutting-edges and the relieved-edges of those arcuate lengths of the cutting-thread which are between the opposite end of the thread and medially of its length.

7. In a threading tool, an annulus having a cutting-thread interrupted at circumferentially spaced points so as to denne arcuate lengths of the cutting-thread' between circumferentially next-adjacent interruptions, the annulus being adapted for axially-reversible rotatable mounting for use of one end or the other of the cuttingthread of the rotatable annulus, the arcuate lengths of the cutting-threadl having cuttings edges at one end, with the cutting-edges of these arcuate lengths of the cutting-thread which are between one end of the thread and medially of `its length, circumferentially reversed with re`ia-= tion to the cutting-edges oi? those arcuate lengths of the cutting-thread which arebetween the ep poslte end of the thread and medially of length.

8. In a threading tool, a tool shank, an annulus having a cutting-thread at its external periphery, the tool shank and the bore of the annulus 'comprising cooperating bearing surfaces adaptis vadjacent respective ends of the annulus wheny the latter is in its respective axially reversed positions, means on the tool shank and the annulus, cooperating when the annulus is in either of its axially reversedv positions, .for fixing the annulus against rotation relative to the tool shank when said annulus is relatively axially displaced in one direction, said means permitting relative axial displacement of the annulus in the opposite directionand being adapted for release responsive to said last mentioned relative axial displacement, and a clutch operable when the annulus is in either'of its axially reversed positions, said clutch comprising a groove in the bearing surface of the tool shank tapering in depth` circumferentially of the annulus, and a roller in said tapering groove binding the annulus against rotation relative to the tool shank in one direction but releasing the annulus for relative rotation in the opposite direction.

9. In a threading tool, a tool shank, an annulus having a cutting-thread at its external periphery, the tool shank and the bore of the in one direction, said means permitting relative axial displacement of the annulus in the opposite direction and being adapted for release responsive to said last mentioned relative axial displacement, and a clutch between the cooperating bearing surfaces and surrounded by the annulus when the. latter is in either of its axially reversed positions, for binding the annulus against rotation relative to the tool shank in one direction but releasing the annulus for relative rotationin the opposite direction.

HARDING F. BAKEWELL. 

